Effect of performance level on the longitudinal electromyographic activity of vastus medialis and vastus lateralis muscles after induced extreme fatigue with a workload of 30 repetition maximum

Abstract

CONTEXT: The study of longitudinal electromyographic (EMG) activity of the muscles under extreme fatigue conditions has been an inadequately explored area in muscle fatigue research. AIMS: The aim of this study was to assess the effect of performance level on the longitudinal EMG activity of the vastus medialis (VM) and vastus lateralis (VL) after induced extreme fatigue with a workload of 30 repetition maximum (RM). DESIGN: This was a cross-sectional study. MATERIALS AND METHODS: Eighteen healthy intercollegiate level male sportspersons (age: 19.84 ± 2.1 years, height: 171.38 ± 8.48 cm, and weight: 69.72 ± 13.85 kg) were randomly selected as participants. As fatigue protocol, 30 repetitions of leg extension exercise with 30 RM load were performed. Isometric contraction of VM and VL muscles at an angle of 0°–10° with 30 RM load was performed until failure as the postfatigue or extreme fatigue protocol. Both protocols were performed in Cybex VR1 leg curl exercise device. EMG activity was recorded from VL and VM during the postfatigue protocol. EMG data were acquired using a 4-Channel Wireless EMG BIOPAC Inc. MP150 system. A criterion called relative impulse (RI) was developed. Based on the magnitude of RI of participants, nine participants were enlisted and equally divided into high-performance (HP) group, mid-performance (MP) group, and low-performance (LP) group. The raw EMG signals were quantified through MATLAB to derive root mean square (RMS) and median frequency (MDF). STATISTICAL ANALYSIS USED: One-way ANOVA and least significant difference (at P RESULTS: All the groups displayed a constant linear trend in regard to MDF and RMS except for the HP group in the VL and LP groups in VM. The EMG activities of all the groups were not significantly different from each other under extreme fatigue. However, muscle activation of VM and VL was significantly different from each other in the MP and LP groups. CONCLUSIONS: Findings are useful for further understanding muscle fatigue.